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Vikram Paranjpe, Nawajes A Mandal, Jeremy Tan, Jason Nguyen, John Yohan Lee, Anat Galor; Associations between meibum quality and sphingolipid quantity and composition. Invest. Ophthalmol. Vis. Sci. 2018;59(9):4892.
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Sphingolipids are important cellular lipids with roles in cell signaling and are significantly associated with many inflammatory and degenerative diseases. The association of sphingolipid composition in human meibum with clinical markers of dry eye has not been studied. We analyzed sphingolipid quantity and composition in human subjects to determine associations with clinically graded meibum quality.
Forty-three subjects underwent a tear film assessment which included clinical grading of meibum quality. Meibum was collected via cotton swab and analyzed with liquid chromatography-mass spectroscopy (LC-MS/MS) for quantitative estimation of various sphingolipid classes and species. Concentration (ρmol) of total sphingolipid (SPL), Ceramide (Cer), Hexosyl-Ceramide (Hex-Cer), Sphingomyelin (SM), Sphingosine (Sph) and Sphingosine 1-phosphate (S1P) was calculated. Composition of SPL was assessed via mole percent of major classes such as Cer, Hex-Cer, and SM. Finally, composition of Cer, Hex-Cer, and SM was assessed via mole percent of 10 individual species. Associations between SPL composition and meibum quality were assessed via Mann-Whitney U and independent samples T-tests, as appropriate.
22 subjects were characterized as having good quality meibum (score of 0 or 1) and 21 were characterized as having poor quality meibum (score of 2, 3 or 4). Subjects with poor quality were older (60 ± 8 years) than those with good quality (51 ± 16 years) and more likely to be male (90% vs 64%). Race and ethnicity profiles were comparable between the two groups. Overall, we found that subjects with poor quality had a lower median concentration (ρmol) of SPL (148.7 vs 234.8, p>0.05), Cer (7.0 vs 83.2, p=0.02), Hex-Cer (7.0 vs 24.4, p=0.03), Sph (2.2 vs 6.0, p>0.05), and S1P (0.15 vs 1.0, p=0.04), and higher median concentration (ρmol) of SM (125.6 vs 66.9, p>0.05). Analysis of mole percent revealed that subjects with poor quality had less Cer (5.7% vs 31.9%, p<0.0005), less Hex-Cer (5.7% vs 10.0%, p=0.01) and more SM (88.6% vs 53.1%, p=0.001). Differences in mole percent of many individual species were found between the two groups. Notably, 26-carbon (26:0) Cer (1.7% vs 0.4%, p=0.02), Hex-Cer (1.7% vs 0.5%, p=0.003), and SM (2.3% vs 0.6%, p>0.05) increased in subjects with poor quality meibum.
Our results indicate that poor meibum quality is significantly associated with compositional changes in meibum.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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